It could be years, maybe even decades, before you regularly catch rides in a completely self-driving car.

But semi-autonomous features, which can take over for a driver in more limited ways and have been available for years in some luxury cars, are making their way into mainstream vehicles. Some midrange cars will automatically brake if they sense an imminent collision, steer back into a freeway lane if the driver allows them to drift, and guide themselves into tight parking spaces.

“We’re definitely in a state right now where we’re starting to see these features become more common in mainstream cars,” said Ed Kim, who keeps tabs on automotive trends as an analyst for AutoPacific, an automotive research and consulting firm.

Such semi-autonomous features have been in the news lately after a fatal crash last month involving a Tesla Model S that was operating with Autopilot. Tesla has touted Autopilot, which can do things like automatically adjust a car’s speed to match traffic and switch lanes by itself when a driver puts on a turn signal, as an example of its cutting-edge technology.

But you don’t have to spend $70,000 for a Model S to get access to such features. I recently got a taste of what’s available in mainstream cars when I test drove a 2017 Ford Fusion Energi, the plug-in model of the company’s midline sedan, which is $40,000, fully loaded.

All of the self-driving technologies that Ford makes available on its Ford or Lincoln models — which include automatic braking, advanced adaptive cruise control, assisted parking and automated lane keeping — are available as options on the Fusion Energi and come standard on the top-of-the-line model.

In testing the various semi-autonomous features on the Fusion, I was struck by how much they varied in terms of usability, polish and reliability.

The most impressive function by far was its advanced adaptive cruise control, a new feature with this year’s model. Adaptive cruise control will try to maintain a set speed, but will automatically slow down if the cars in front of you decelerate and will accelerate back when they speed up.

The Fusion’s system takes this technology a step further, because unlike those on other cars, it will continue to work in stop-and-go traffic. Using radar and a camera system placed behind the rearview mirror to detect vehicles in front of it, it will bring you to a complete stop in a traffic jam and then re-accelerate as traffic resumes.

It worked great. I hate being stuck in traffic, but having a system that could take over the braking and accelerating made it much more bearable. There were a few times I got nervous, because I could tell that cars that were several vehicles ahead of me were starting to brake and the Fusion didn’t realize yet that it needed to slow down. But it kept a good following distance and always decelerated in plenty of time.

Somewhat less impressive was the Fusion’s parking system. That function will take control of the steering wheel and, using ultrasonic sensors to detect nearby vehicles, will guide the car into a parallel or perpendicular spot, telling you when to press the accelerator or brake.

The parking system doesn’t detect the lines marking out a parking spot. If it doesn’t have at least one parked car to guide it, it won’t be able to steer you into a spot. When it detects a spot, though, it generally works well.

But it’s slow. In my tests, the Fusion sometimes required a five- or even a seven-point turn to back into a perpendicular spot. It was faster with parallel ones. But, unless you’re terrible at parking, you’re likely to do both much quicker on your own.

Even less impressive was the Fusion’s lane-keeping system, which is also new to the car. The same camera used in the adaptive cruise control system is supposed to keep track of lane lines as you are driving. If you start to drift out of your lane, the system can be set to slightly turn the steering wheel to get you back on track.

But in my tests, the lane-keeping system rarely worked. I would intentionally let the car drift — making sure there were no cars around me first, of course — but instead of steering me straight, it usually just let me glide on into the next lane. I had little confidence that the system would keep me out of an accident.

The car’s automatic braking feature also gave me pause. Relying on the same radar-and-camera system used for adaptive cruise control, the braking system is designed to warn you — by lighting up a bar of red LED lights on the dashboard — if it thinks you are in danger of a collision and to automatically try to stop the car if you don’t quickly apply the brakes or steer out of danger.

That feature was hard to test, for obvious reasons — I didn’t want to take a chance of plowing into something. But on a couple of occasions, the feature’s warning light went off in a way that both surprised and worried me.

In one particular case, the automatic braking system seemed to fear I was going to collide with a car that was stopped in the left-hand lane while waiting to turn. My car, which was in the right-hand lane, was indeed headed straight for it, but my lane curved out of the way as it approached the car. The braking system didn’t attempt to stop my car, but the warning worried me; there were cars behind me and if the system had automatically applied the brakes, it could have caused more danger than it prevented.

That was unlikely to happen, said Scott Lindstrom, Ford’s driver assist technology manager. The automatic braking system only gets triggered when a collision appears imminent; in its most sensitive setting, it can give a warning a second or more before the brakes get applied. That’s likely what happened in my case, he said.

Still, as my experience indicated, even though semi-autonomous functions are becoming more widely available, many of them could use some more work.

Troy Wolverton writes the Tech Files column and covers consumer technology as the personal technology columnist for the Bay Area News Group. Previously, he covered Apple and the consumer electronics industry. Earlier, he reported on technology, business and financial issues for TheStreet.com and CNET News.com.